A pharmaceutical form for the rectal administration of pharmacologically active compounds

Abstract: A pharmaceutical form for rectal administration consisting of a sheath (1) of gelatine containing: (a) one or more capsules (3) made of a mixture of gelatine and glycerine, for example in a quantity by weight of approximately 70% of gelatine and 30% of glycerine, (b) one or more supports, such as tablets (2), containing the active agent, the supports being non-liquid.

Description: This invention relates to a new pharmaceutical form for the rectal administration of pharmacologically active compounds. The rectal administration of pharmacologically active molecules is widely used. This form of administration has the advantage over oral administration that it is unaffected by the ingestion of foods, nausea or low intestinal absorption. On the other hand, this form of administration can be used in patients who are incapable of salivating, who are unconscious or who have to go without food before an operation. Published European Patent Application EP-A-0 147 479 describes a water and drug delivery system for suppository use. The subject-matter of the application relates to pharmaceutical forms for the rectal administration of active ingredients comprising an aqueous core in a waxy housing, surrounded by a matrix, which comprises a drug, located in the matrix itself, water soluble or dispersible excipients, such as polyethylene glycol, gelatin, starch, lactose or cellulosic derivatives, osmotic-active agents, absorption promoter and a coating, which coating is a semi-permeable film, selected from cellulose acetate, polyvinyl acetate and ethylene vinyl acetate. The matrix, in which the active agent is located, gives the drug delivery system shape, rigidity and preserves the integrity of the device prior to use. Nevertheless, since the rectum is made up of zones differing in their characteristics, the effects of treatment by rectal administration vary according to the pharmaceutical forms used and their anatomical positioning. Thus, the positioning of a pharmaceutical form in the lower part of the rectum enables the active principle which it contains to pass directly into the general circulation. Forms positioned in the upper or middle part of the rectum enable the active principles which they contain to pass into the portal system. In that case, the active principle is in danger of undergoing metabolic degradation in the liver. Forms which provide for specific administration in the lower part of the rectum have already been described in the prior art literature. They have outer surfaces comprising bioadhesive substances which facilitate their retention by the layer of mucus covering that part, this retention preventing the pharmaceutical form from moving towards the upper parts of the rectum. Suppositories containing fats are unsuitable for this application because they cannot be retained in the lower part of the rectum on account of their composition. Suppositories made of hydrogels, such as polyethylene glycol, which are impregnated with pharmacologically active substances have also been described (Cole et al., Br J. Clin. Pharmac. 1990, 30, 781-786). Gelatine sheaths containing various active principles have also been tested for rectal administration. These sheaths are positioned in the lower part of the rectum where they deliver the active principle which they contain (Brumley et al., The Hospice Journal, Vol. 4(1) 1988; Maloney et al., The American Journal of Hospice Care, July/August 1989, 6(4), 34-35). These pharmaceutical forms allow the active principle to pass into the circulation without being metabolized by the liver. Nevertheless, this type of pharmaceutical form is variously accepted by patients with dry rectal mucosa and does not meet all the requirements of treatments involving this method of administration. Accordingly, applicants set out to find pharmaceutical forms which, even in the event of drying out, would provide for improved absorption by the rectal mucosa of the active principle present in the pharmaceutical forms. According to the invention, it has surprisingly been found that pharmaceutical forms containing large quantities of hygroscopic substances, i.e. substances establishing a supply of water at the level of the rectal mucosa, enable better passage of the active principle into the circulation to be obtained while maintaining effective hydration of the mucosa. It has also been found that the supply of water established by the presence of hygroscopic substances enabled the pH of the mucosa to be reduced to optical values for the passage of certain active principles. Accordingly, the present invention relates to a pharmaceutical form for the rectal administration of at least one pharmacologically active compound assimilable in the lower part of the rectum, the said pharmaceutical form consisting of a sheath of which the outer wall comprises a material with bioadhesive properties, the interior of the sheath containing the combination of: (a) at least one capsule containing at least one hygroscopic substance and (b) an effective quantity of the said compound in a non-liquid form. In order to establish a supply of water, the said pharmaceutical form contains significant quantities of hygroscopic substances (a). The ratio by weight of the quantities of hygroscopic substances contained in the sheath and capsules to the quantities of non-hygroscopic substances is advantageously at least 1.5 and preferably at least 2. One such pharmaceutical form may thus contain a quantity of hygroscopic substances of at least 400 mg and preferably 600 mg per dosage unit. The hygroscopic substances may be gelatine or glycerine used individually or in the form of a mixture or any hygroscopic substance compatible with pharmaceutical formulations. The constituent material of the wall of the sheath is gelatine while the capsule(s) comprise a mixture of gelatine and glycerine. The supply of water established by the proteins forming the membrane of the sheath and the hygroscopic capsules has the effect of reducing or maintaining the pH of the rectal mucosa which is favorable to the rectal administration of numerous active principles. The absorption of compounds of this type and their passage into the circulation are thus increased. The quantity of active agent present in the pharmaceutical form according to the invention varies according to the nature of the active agent and the desired posology. For example, for the speciality Carlytene or Moxisylyte, see Vidal, 1992, page 234), the quantity of active agent per dose may be between 30 and 500 mg and, for the speciality Azelastine (see Merck Index, 11th Ed., page 926, No. 922), the quantity of active agent per dose may be between about 2 and 12 mg. In an even more preferred embodiment, the pharmaceutical form consists of a sheath of gelatine, the sheath containing: (a) one or more capsules consisting of a mixture of gelatine and glycerine, (b) one or more vehicles or supports containing the active agent, the supports being non-liquid. In one particular embodiment, the proportions by weight in the capsules are of the order of 70% of gelatine and 30% of glycerine. One particularly simple embodiment of the support consists of one or more tablet(s) containing the active agent which are accommodated in the sheath. The following examples use tablets although the invention is by no means confined to such supports. It is also possible to use microgranules containing the active agent which are either free or accommodated in a sheath. The expression "tablets" also encompasses pellets, pills and other solid galenic forms typically used for the presentation of pharmaceutically active agents. The pharmaceutically active agents in particular may also be contained in gels. The arrangement of the supports and capsules in the sheath may vary according to the desired characteristics of the pharmaceutical form. Illustrative examples are provided in the following with reference to Figures 1, 2 and 3 of the accompanying drawings. It is pointed out that the total quantity of hygroscopic substances present in the pharmaceutical form according to the invention should be such that it is capable of establishing a supply of water providing for sufficient hydration of the rectal mucosa although it should not be excessive in order to avoid a laxative effect. In the context of the invention, a bioadhesive material is any substance which enables the pharmaceutical forms to adhere to the rectal mucosa. In the case of gelatine, the required adhesiveness may be established by contact and interpenetration of the gelatine chains with the mucus and then by coupling of the gelatine and mucus. The principle advantages of the pharmaceutical forms according to the invention are as follows: because they are administered by the rectal route, they do not undergo any modification during digestion and cannot be rejected by the patients, for example in the event of vomiting: they may readily be administered to patients who cannot be treated by oral administration, particularly in cases of cancer of the upper aerodigestive tracts; in the event of overdosage, the pharmaceutical forms may readily be eliminated by washing; the pharmacologically active molecules are not metabolized by the liver by virtue of their passage through the portal system. In addition, the pharmaceutical forms according to the invention have specific advantages, namely: they have a better delayed-release effect than other rectal forms which enables them to be administered to patients every 24 hours and not every 12 hours or even less as is the case with the other rectal forms; they show better reproducibility in regard to absorption of the active principle both in various patients and in the event of repeated treatments for one and the same patient; by virtue of the buffering capacity of the proteins constituting the gelatine of the sheaths, they enable the pH to be maintained in an optimal absorption window of the pharmacologically active compound with which it is desired to treat the patient. The present invention lends itself to the formulation of numerous types of pharmaceutically active agents suitable for rectal administration. Non-limiting examples are provided hereinafter. The preferred category of active compounds is that of so-called matrix compounds in which the active agent is trapped in a polymer network from which it escapes slowly. The expert is thus in a position to determine the active agents which are suitable for carrying out the invention. Supports, particularly tablets, having a delayed-release effect are generally preferred. Thus, the sustained-release dihyrocodeine tablets marketed in France under the name of "Dicoda" may be used in the pharmaceutical form according to the invention. The invention is illustrated by the following non-limiting examples in conjunction with the accompanying drawings, wherein: Figure 1 shows a sheath containing two tablets and two capsules each occupying part of the sheath. Figure 2 shows a pharmaceutical form in which the sheath contains two tablets sandwiched between two capsules. Figure 3 illustrates a variant of Fig. 2 in which one to three tablets are accommodated in a sheath between two capsules. In the pharmaceutical form shown in Fig. 1, the sheath (1) comprises two tablets (2) of pharmaceutically active compound and two hygroscopic capsules (3), the tablets and the capsules each occupying part of the sheath. Figure 2 shows a pharmaceutical form in which the sheath (1) comprises two tablets (2) sandwiched between two capsules (3). In this case, the introduction of the sheath into the rectum - in addition to dissolution of the sheath - allows the formation of an amalgam between the capsules and the tablets by softening of the capsules. This amalgam delays the release of the pharmaceutically active compound and thus further improves the sustained release effect of the pharmaceutical form according to the invention. Figure 3 shows a pharmaceutical form in which the sheath (1) comprises two capsules (3) arranged at either end of the sheath and one to three tablets (2) of active principle between the capsules. The following examples are intended to illustrate the invention without limiting it in any way. Tests were carried out with size OO rectal sheaths containing two gelatine capsules each weighing 266 mg. Two active principles were tested, namely Carlytene in the form of 30 mg tablets and Azelastine in the form of 4.4 mg tablets. Two arrangements in the sheath were studied, namely: the tablets are surrounded by the soft capsules in the following arrangement: capsule - tablet - capsule (c-cp-c for short), cf. Fig. 3; the tablets are only in contact with a single soft capsule in the following arrangement: capsule - capsule - tablet (c-c-cp for short), cf. Fig. 1. The tests comprised measuring the percentage of active principle (AP) released by dissolution as a function of time (in minutes). The procedure adopted for dissolution is described in Pharmacopée Européenne, 2nd Edition, Part 1, V.5.4. The working conditions were as follows: 1) CARLYTENE 30 mg temperature: 37°C medium: 500 ml water 1 tablet per reactor rotational speed of the blades 50 r.p.m. DO reading at 274 nm every 5 minutes 2) AZELASTINE 4.4 mg temperature: 37°C medium: 500 ml 0.01 N HCl 2 tablets per reactor rotational speed of the blades 100 r.p.m. DO reading at 285 nm every 5 minutes The results obtained are set out in Tables I and II below. N.B.: With the single tablet, the AP release rate was 80% in 5 to 7 minutes. N.B.: With the single tablet, the AP release rate was 80% in less than 15 minutes. The rectal administration of pharmaceutical forms according to the invention thus provides for a greater delayed-release effect and for smaller variations in the concentration of active agent in the plasma. Thus, the pharmaceutical form according to the invention enables active compounds to be administered to patients at longer intervals of the order of 24 hours for the same average activity. This advantage is reflected in improved comfort both for the patient and for the nursing personnel.

Claims: A pharmaceutical form for the rectal administration of at least one pharmacologically active compound assimilable in the lower part of the rectum, with at least one pharmacologically compound and water-soluble and/or dispersible excipients in the interior of a coating, characterized in that the said pharmaceutical form consists of a sheath of which the outer wall comprises a material with bioadhesive properties, the interior of the sheath contains side by side available the combination of: (a) at least one capsule containing at least one hygroscopic substance and (b) an effective quantity of the said compound in a non-liquid form. A pharmaceutical form as claimed in claim 1, characterized in that the ratio by weight of the quantities of hygroscopic substances contained in the sheath and the capsules to the quantities of non-hygroscopic substances is at least 1.5 and preferably at least 2. A pharmaceutical form as claimed in claim 1 or 2, characterized in that the quantity of hygroscopic substances is at least 400 mg and preferably 600 mg per dosage unit. A pharmaceutical form as claimed in any of claims 1 to 3, characterized in that the active compound is present in a support, advantageously a delayed-release support, such as tablets, microgranules, either free or accommodated in a sheath, gels and the like. A pharmaceutical form as claimed in any of claims 1 to 4, characterized in that the active compound is in the form of matrix compounds in which the active agent is trapped in a polymer network from it escapes slowly. A pharmaceutical form as claimed in any of claims 1 to 5, characterized in that the bioadhesive material is gelatine. A pharmaceutical form as claimed in any of claims 1 to 6, characterized in that the capsule is made of gelatine, glycerine and advantageously a mixture of gelatine and glycerine. A pharmaceutical form as claimed in any of claims 1 to 7, characterized in that it consists of a sheath (1) of gelatine containing: (a) one or more capsules (3) made of a mixture of gelatine and glycerine, for example in a quantity by weight of approximately 70% of gelatine and 30% of glycerine, (b) one or more supports, such as tablets (2), containing the active agent, the supports being non-liquid. A pharmaceutical form as claimed in any of claims 1 to 8, characterized in that the supports are sandwiched between two capsules. A pharmaceutical form as claimed in any of claims 1 to 8, characterized in that the supports are accommodated in the sheath either between or adjacent the capsules.

Inventors: GRISLAIN LUC, LE HUEDE ELISABETH, LOUIS OLIVER, GRISLAIN, LUC, LE HUEDE, ELISABETH, LOUIS, OLIVER
Applicants: ASTA MEDICA AG, ASTA MEDICA AKTIENGESELLSCHAFT
Application year: 1994
Main classification: A61K9
IPC codes: A61K9